From a different point of view, Bergeret et al. suggested that an odd-frequency pair amplitude is induced
near the interface between superconductor and ferromagnet.
[1]}, [2]}, [3]}, [4]}, [5]}, [6]}, [7]}
Since the magnetic field from the ferromagnet modifies the spin-part wavefunction of the Cooper pair,
it leads to a mixing between the singlet and triplet parings and induces the odd-frequency pair amplitude.
It was also pointed out by Tanaka et al. that the odd-frequency amplitude is present
also in the vicinity of boundaries in unconventional superconductors.
[8]}, [9]}, [10]}, [11]}.
In this case, the even- and odd-parities of the Cooper pair are mixed by the broken translational symmetry.
This parity mixing is also present around a vortex core and induces the odd-frequency amplitude there.
[12]}, [13]}
